Plant dye used to create green lithium-ion battery

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The madder plant has been grown and used for centuries as its root can be boiled down to create orange, red, and pink fabric dye called purpurin. But researchers have now discovered purpurin can be used to help create a sustainable, non-toxic lithium-ion rechargeable battery.

The cathodes used in existing lithium-ion batteries rely on metal ores, with cobalt being a main ingredient. As well as having to mine the cobalt, the process of combining cobalt salt with lithium requires very high temperatures, and therefore energy. So producing a battery also produces a high amount of carbon.

The research team, which is a collaboration between The City College of New York, Rice University, and the US Army Research Laboratory, have estimated that 72kg of carbon dioxide are produced for every kilowatt hour of energy in existing Li-on batteries. By replacing cobalt with purpurin, that would no longer be the case.

As purpurin is grown, the madder plant will actually take carbon dioxide out of the atmosphere rather than producing more of it. The process of combining purpurin with lithium salt can also be done at room temperature using alcohol solvent, so no energy is required to achieve high temperatures as with cobalt. And the final benefit is to do with recycling. As there’s no toxic components, the batteries can more easily be recycled or discarded.

Apparently the process works so effectively it’s a case of when, not if purpurin will replace cobalt in lithium-ion batteries. The researchers still have work to do on increasing efficiency, but they say commercial green lithium-ion batteries are only a few years away.

Using plant matter to enhance batteries isn’t a new idea. We’ve already heard about a plant virus that makes lithium-ion batteries last 10x longer, and seaweed that could give batteries a green power boost. It seems any future battery tech we use will rely on material being grown rather than mined, which is great news for the environment.